NREL/NASA Internal Short-Circuit Instigator in Lithium Ion Cells: NREL (National Renewable Energy Laboratory)

NREL has developed a device to test one of the most challenging failure mechanisms of lithium-ion (Li-ion) batteries -- a battery internal short circuit. Many members of the technical community believe that this type of failure is caused by a latent flaw that results in a short circuit between electrodes during use. As electric car manufacturers turn to Li-ion batteries for energy storage, solving the short circuit problem becomes more important. To date, no reliable and practical method exists to create on-demand internal shorts in Li-ion cells that produce a response that is relevant to the ones produced by field failures. NREL and NASA have worked to establish an improved ISC cell-level test method that simulates an emergent internal short circuit, is capable of triggering the four types of cell internal shorts, and produces consistent and reproducible results. Internal short circuit device design is small, low-profile and implantable into Li-ion cells, preferably during assembly. The key component is an electrolyte-compatible phase change material (PCM). The ISC is triggered by heating the cell above PCM melting temperature (presently 40 degrees C -- 60 degrees C). In laboratory testing, the activated device can handle currents in excess of 300 A to simulate hard shorts (< 2 mohms). Phase change from non-conducting to conducting has been 100 percent successful during trigger tests.